The use of inhalation devices in the administration of medicaments, for example in bronchodilation therapy is well known. Such devices generally comprise a body or housing within which a medicament carrier is located. Known inhalation devices include those in which the medicament carrier is a blister pack containing a number of blister pockets for containment of medicament in dry powder form. Such devices typically contain a mechanism for accessing a medicament dose by opening one or more blister pockets. The mechanism for example, comprises either piercing means or peeling means to peel a lid sheet away from a base sheet of the blister pack. The powdered medicament is then liberated from the opened blister pocket(s) for inhaled delivery to the patient.
Inhalation devices of the type described above comprise an element, generally referred to as a manifold, for guiding airflow towards one or more opened blister pocket(s) for liberating the powder contained therein; and subsequently guiding that liberated powder to a mouthpiece for inhalation by a patient. It is appreciated that the characteristics of the manifold are important in both ensuring effective liberation of powder and in subsequent guiding that liberated powder to the mouthpiece.
The Applicant has now appreciated that the form of the manifold can affect the particle size characteristics of the liberated medicament powder, which characteristics are known to be pharmaceutically important. In particular, the Applicant has appreciated that fine particle fraction can be influenced by the form of the manifold. As known in the art, “fine particle fraction” or FP Fraction generally refers to the percentage of particles within a given dose of aerosolized medicament that is of “respirable” size. It is desirable that the form of the manifold acts such as to increase the FP Fraction of the liberated powder that is made available at the mouthpiece for inhalation by the patient.
In one aspect, the Applicant has now found that manifold performance, and potentially FP fraction performance, is enhanced if the manifold is arranged such as to delay the emptying of the medicament powder from the blister pocket. Suitably, emptying of the medicament powder from the blister pocket is delayed until one or more regions of differential force (e.g. high shear) are established in a chamber of the manifold through which the medicament powder is subsequently transported (e.g. entrained in an airflow).